Caffeine is one of the most commonly used stimulants among athletes. Taking caffeine, within limits, is allowed by the National Collegiate Athletic Association (NCAA). Urine concentrations over 15 mcg/mL are prohibited. It takes most people about 8 cups of coffee providing 100 mg/cup to reach this urine concentration.

In foods, caffeine is used as an ingredient in soft drinks, energy drinks, and other beverages.

People with voice disorders, singers, and other voice professionals are often advised against using caffeine. However, until recently, this recommendation was based only on hearsay. Now developing research seems to indicate that caffeine may actually harm voice quality. But further study is necessary to confirm these early findings.

How does it work?

Caffeine works by stimulating the central nervous system (CNS), heart, muscles, and the centers that control blood pressure. Caffeine can raise blood pressure, but might not have this effect in people who use it all the time. Caffeine can also act like a “water pill” that increases urine flow. But again, it may not have this effect in people who use caffeine regularly. Also, drinking caffeine during moderate exercise is not likely to cause dehydration.

CAFFEINE Uses & Effectiveness

Migraine headache. Taking caffeine by mouth together with painkillers such aspirin and acetaminophen is effective for treating migraines. Caffeine is an FDA-approved product for use with painkillers for treating migraine headaches.

Headache following surgery. Using caffeine by mouth or intravenously (by IV) is effective for preventing headaches following surgery. Caffeine is an FDA-approved product for this use in people who regularly consume products that contain caffeine.

Tension headache. Taking caffeine by mouth in combination with painkillers is effective for treating tension headaches.

Mental alertness. Research suggests that drinking caffeinated beverages throughout the day keeps the mind alert. Combining caffeine with glucose as an “energy drink” seems to improve mental performance better than either caffeine or glucose alone.

Asthma. Caffeine appears to improve airway function for up to 4 hours in people with asthma.

Athletic performance. Taking caffeine seems to increase physical strength and endurance and might delay exhaustion. It might also reduce feelings of exertion and improve performance during activities such as cycling, running, playing soccer, and golfing. However, caffeine does not seem to improve performance during short-term, high-intensity exercise such as sprinting and lifting.

Diabetes. Drinking beverages that contain caffeine is linked with a lower risk of developing type 2 diabetes. It appears that the more caffeine that is consumed, the lower the risk. Although caffeine might help prevent type 2 diabetes, it might not be effective in treating type 2 diabetes. Research on the effects of caffeine in people with type 1 diabetes is inconsistent. Some research shows benefit, while other research does not.

Gallbladder disease. Drinking beverages that provide at least 400 mg of caffeine daily seems to reduce the risk of developing gallstone disease. The effect seems to be dose-dependent. Taking 800 mg of caffeine daily seems to work best.

Memory. Taking 200 mg of caffeine by mouth daily seems to improve memory in some people with outgoing personalities and college students.

Breathing problems in infants. Caffeine given by mouth or intravenously (by IV) appears to improve breathing in infants born too early. It seems to reduce the number of episodes of shortness of breath by at least 50% over 7-10 days of treatment. However, caffeine does not seem to reduce the risk of premature infants developing breathing problems.

Pain. Research suggests that taking caffeine together with painkillers can reduce pain.

Parkinson’s disease. Some research suggests that people who drink caffeinated beverages have a decreased risk of Parkinson’s disease. However, this reduced risk is not observed in people who smoke cigarettes.

Headache after epidural anesthesia. Taking caffeine by mouth or intravenously (by IV) seems to help prevent headache after epidural anesthesia

Weight loss. Taking caffeine in combination with ephedrine seems to help reduce weight, short-term. Taking 192 mg of caffeine in combination with 90 mg of ephedra daily for 6 months seems to cause a modest weight reduction (5.3 kg or 11.66 pounds) in overweight people. This combination, along with limiting fat intake to 30 percent of calories and moderate exercise, also seems to reduce body fat, decrease “bad” low-density lipoprotein (LDL) cholesterol, and increase “good” high-density lipoprotein (HDL) cholesterol. However, there can be unwanted side effects. Even in carefully screened and monitored otherwise healthy adults, caffeine/ephedra combinations can cause changes in blood pressure and heart rate.

Attention deficit-hyperactivity disorder (ADHD). Most research suggests that caffeine does not reduce ADHD symptoms in children. The use of caffeine in adolescents and adults with ADHD has not been studied.

Depression. Some research suggests that caffeine intake is linked with an increased occurrence of depression symptoms in children. However, other research suggests that caffeinated coffee intake is linked to a decreased occurrence of depression in adults.

Low levels of oxygen in the blood caused by exercise. Early research shows that taking caffeine may improve breathing during exercise, but does not affect blood levels of oxygen in athletes with low blood oxygen levels during exercise

Hepatitis C. Research suggests that higher intake of caffeine from coffee is linked to reduced liver scarring in people with hepatitis C.

Headaches while sleeping. Some early evidence suggests that drinking a cup of coffee before bed or upon waking up might help alleviate pain associated with headaches that occur during sleep.

Cramping due to narrowed arteries (intermittent claudication). Taking a single 6 mg dose of caffeine by mouth seems to improve walking and muscle strength in people with aching and cramping due to narrowed or blocked arteries.

Liver cirrhosis. Research suggests that drinking coffee might reduce the risk for liver cirrhosis. However, it is unclear if this effect is due to caffeine or other components of coffee.

Muscle soreness during exercise. Evidence on the effect of caffeine for muscle soreness during exercise is inconsistent. It seems that taking moderate doses of caffeine (10 mg/kg) can reduce muscle pain during exercise, while lower doses may not have this effect.

Obsessive-compulsive disorder (OCD). Early research shows that adding caffeine to conventional therapy seems to decrease the severity of OCD symptoms.

Stoke. Research shows that increased caffeinated or decaffeinated coffee intake is linked to a decreased risk of stroke in women. However, it is not clear if the effect is due to caffeine.

Skin irritation, redness, and itching.

Overdose.

Other conditions.

More evidence is needed to rate caffeine for these uses.

CAFFEINE Side Effects & Safety

Caffeine is LIKELY SAFE for most adults when used appropriately.

Caffeine is POSSIBLY UNSAFE when taken by mouth for a long time or in fairly high doses. Caffeine can cause insomnia, nervousness and restlessness, stomach irritation, nausea and vomiting, increased heart rate and respiration, and other side effects. Caffeine can make sleep disorders in patients with acquired immunodeficiency syndrome (AIDS) worse. Larger doses might cause headache, anxiety, agitation, chest pain, and ringing in the ears.

Caffeine is LIKELY UNSAFE when taken by mouth in very high doses as it can cause irregular heartbeats and even death.

Special Precautions & Warnings:

Children: Caffeine is POSSIBLY SAFE when taken appropriately by mouth or intravenously (by IV), as well as when used in amounts commonly found in foods and beverages.

Pregnancy and breast-feeding: Caffeine is POSSIBLY SAFE in pregnant or breast-feeding women when used daily amounts of less than 200 mg. This is about the amount in 1-2 cups of coffee. Consuming larger amounts during pregnancy or when breast-feeding is POSSIBLY UNSAFE. When consumed in larger amounts during pregnancy, caffeine might increase the chance of miscarriage and other problems. Also, caffeine can pass into breast milk, so nursing mothers should closely monitor caffeine intake to make sure it is on the low side. High intake of caffeine by nursing mothers can cause sleep disturbances, irritability, and increased bowel activity in breast-fed infants.

Anxiety disorders: Caffeine might make these conditions worse. Use with care.

Bipolar disorder: Too much caffeine might make this condition worse. In one case, a 36-year-old man with controlled bipolar disorder was hospitalized with symptoms of mania after drinking several cans of an energy drink containing caffeine, taurine, inositol, and other ingredients (Red Bull Energy Drink) over a period of 4 days. Use caffeine with care and in low amounts if you have bipolar disorder.

Bleeding disorders: There is concern that caffeine might aggravate bleeding disorders. Use caffeine with care if you have a bleeding disorder.

Diabetes: Some research suggests that caffeine may affect the way the body uses sugar and might worsen diabetes. However, the effect of caffeinated beverages and supplements has not been studied. If you have diabetes, use caffeine with caution.

Diarrhea: Caffeine, especially when taken in large amounts, can worsen diarrhea.

Epilepsy: People with epilepsy should avoid using caffeine in high doses. Low doses of caffeine should be used cautiously.

Glaucoma: Caffeine increases the pressure inside the eye. The increase occurs within 30 minutes and lasts for at least 90 minutes after drinking caffeinated beverages.

High blood pressure: Consuming caffeine might increase blood pressure in people with high blood pressure. However, this effect might be less in people who use caffeine regularly.

Irritable bowel syndrome (IBS): Caffeine, especially when taken in large amounts, can worsen diarrhea and might worsen symptoms of IBS.

Weak bones (osteoporosis): Caffeine can increase the amount of calcium that is flushed out in the urine. If you have osteoporosis or low bone density, caffeine should be limited to less than 300 mg per day (approximately 2-3 cups of coffee). It is also a good idea to get extra calcium to make up for the amount that may be lost in the urine. Older women with an inherited disorder that affects the way vitamin D is used should use caffeine with caution. Vitamin D works with calcium to build bones.

CAFFEINE Interactions

Stimulant drugs speed up the nervous system. Caffeine and ephedrine are both stimulant drugs. Taking caffeine along with ephedrine might cause too much stimulation and sometimes serious side effects and heart problems. Do not take caffeine-containing products and ephedrine at the same time.

Caffeine might block the effects of adenosine (Adenocard). Adenosine (Adenocard) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop consuming caffeine-containing products at least 24 hours before a cardiac stress test.

Antibiotics (Quinolone antibiotics) interacts with CAFFEINE

The body breaks down caffeine to get rid of it. Some antibiotics might decrease how quickly the body breaks down caffeine. Taking these antibiotics along with caffeine can increase the risk of side effects including jitteriness, headache, increased heart rate, and other side effects.

The body breaks down caffeine to get rid of it. Cimetidine (Tagamet) can decrease how quickly your body breaks down caffeine. Taking cimetidine (Tagamet) along with caffeine might increase the chance of caffeine side effects including jitteriness, headache, fast heartbeat, and others.

Clozapine (Clozaril) interacts with CAFFEINE

The body breaks down clozapine (Clozaril) to get rid of it. Caffeine seems to decrease how quickly the body breaks down clozapine (Clozaril). Taking caffeine along with clozapine (Clozaril) can increase the effects and side effects of clozapine (Clozaril).

Dipyridamole (Persantine) interacts with CAFFEINE

Caffeine might block the affects of dipyridamole (Persantine). Dipyridamole (Persantine) is often used by doctors to do a test on the heart. This test is called a cardiac stress test. Stop consuming caffeine-containing products at least 24 hours before a cardiac stress test.

Disulfiram (Antabuse) interacts with CAFFEINE

The body breaks down caffeine to get rid of it. Disulfiram (Antabuse) can decrease how quickly the body gets rid of caffeine. Taking caffeine along with disulfiram (Antabuse) might increase the effects and side effects of caffeine including jitteriness, hyperactivity, irritability, and others.

Estrogens interacts with CAFFEINE

The body breaks down caffeine to get rid of it. Estrogens can decrease how quickly the body breaks down caffeine. Taking caffeine along with estrogens might cause jitteriness, headache, fast heartbeat, and other side effects. If you take estrogens limit your caffeine intake.

The body breaks down caffeine to get rid of it. Fluvoxamine (Luvox) can decrease how quickly the body breaks down caffeine. Taking caffeine along with fluvoxamine (Luvox) might cause too much caffeine in the body, and increase the effects and side effects of caffeine.

Lithium interacts with CAFFEINE

You body naturally gets rid of lithium. Caffeine can increase how quickly your body gets rid of lithium. If you take products that contain caffeine and you take lithium, stop taking caffeine products slowly. Stopping caffeine too quickly can increase the side effects of lithium.

Medications for depression (MAOIs) interacts with CAFFEINE

Caffeine can stimulate the body. Some medications used for depression can also stimulate the body. Taking caffeine along with some medications for depression might cause serious side effects including fast heartbeat, high blood pressure, nervousness, and others.

Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.

The stimulant effects of caffeine can block the sleep-producing effects of pentobarbital.

Phenylpropanolamine interacts with CAFFEINE

Caffeine can stimulate the body. Phenylpropanolamine can also stimulate the body. Taking caffeine along with phenylpropanolamine might cause too much stimulation and increase heartbeat, blood pressure, and cause nervousness.

Riluzole (Rilutek) interacts with CAFFEINE

The body breaks down riluzole (Rilutek) to get rid of it. Taking caffeine along with riluzole (Rilutek) might decrease how fast the body breaks down riluzole (Rilutek) and increase the effects and side effects of riluzole (Rilutek).

Stimulant drugs interacts with CAFFEINE

Stimulant drugs speed up the nervous system. By speeding up the nervous system, stimulant medications can make you feel jittery and speed up your heart rate. Caffeine might also speed up the nervous system. Taking caffeine along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure. Avoid taking stimulant drugs along with caffeine.

Caffeine works similarly to theophylline. Caffeine can also decrease how quickly the body gets rid of theophylline. Taking theophylline along with caffeine might increase the effects and side effects of theophylline.

Verapamil (Calan, Covera, Isoptin, Verelan) interacts with CAFFEINE

The body breaks down caffeine to get rid of it. Verapamil (Calan, Covera, Isoptin, Verelan) can decrease how quickly the body gets rid of caffeine. Taking caffeine along with verapamil (Calan, Covera, Isoptin, Verelan) can increase the risk of side effects for caffeine including jitteriness, headache, and an increased heartbeat.

The body breaks down caffeine to get rid of it. Alcohol can decrease how quickly the body breaks down caffeine. Taking caffeine along with alcohol might cause too much caffeine in the bloodstream and caffeine side effects including jitteriness, headache, and fast heartbeat.

Birth control pills (Contraceptive drugs) interacts with CAFFEINE

The body breaks down caffeine to get rid of it. Birth control pills can decrease how quickly the body breaks down caffeine. Taking caffeine along with birth control pills can cause jitteriness, headache, fast heartbeat, and other side effects.

Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others.

Fluconazole (Diflucan) interacts with CAFFEINE

The body breaks down caffeine to get rid of it. Fluconazole (Diflucan) might decrease how quickly the body gets rid of caffeine. Taking caffeine along with fluconazole (Diflucan) might cause caffeine to stay in to body too long and increase the risk of side effects such as nervousness, anxiety, and insomnia.

The body breaks down caffeine to get rid of it. Mexiletine (Mexitil) can decrease how quickly the body breaks down caffeine. Taking Mexiletine (Mexitil) along with caffeine might increase the effects and side effects of caffeine.

Terbinafine (Lamisil) interacts with CAFFEINE

The body breaks down caffeine to get rid of it. Terbinafine (Lamisil) can decrease how fast the body gets rid of caffeine. Taking caffeine along with terbinafine (Lamisil) can increase the risk of caffeine side effects including jitteriness, headache, increased heartbeat, and other effects.

CAFFEINE Dosing

The following doses have been studied in scientific research:

BY MOUTH:

For headache or improving mental alertness: 250 mg per day.

For tiredness: 150-600 mg.

For improving athletic performance: 2-10 mg/kg or more has been used. However, doses in excess of 800 mg per day can result in urine levels greater than the 15 mcg/mL allowed by the National Collegiate Athletic Association.

For weight loss: the ephedrine/caffeine combination products are commonly dosed 20 mg/200 mg three times per day.

For headache after epidural anesthesia: 300 mg.

For preventing gallstone disease: intake of 400 mg or more of caffeine per day.

For preventing Parkinson’s disease: men drinking 421-2716 mg of total caffeine daily have the lowest risk of developing Parkinson's disease, when compared to other men. However, men who drink as little as 124-208 mg of caffeine daily also have a significantly lower chance of developing Parkinson's disease. In women, moderate caffeine intake per day (1-3 cups of coffee per day) seems to be best.

One cup of brewed coffee provides from 95-200 mg of caffeine. An 8-ounce serving of black tea provides from 40-120 mg of caffeine. An 8-ounce serving of green tea provides 15-60 mg of caffeine. Soft drinks such as cola provide from 20-80 mg of caffeine per 12 ounce serving. Sports or energy drinks typically provide from 48-300 mg of caffeine per serving.

INTRAVENOUS:

Caffeine is given intravenously (by IV) by healthcare providers for breathing problems in infants and for headache after epidural anesthesia.

Beach, C. A., Bianchine, J. R., and Gerber, N. The excretion of caffeine in the semen of men: pharmacokinetics and comparison of the concentrations in blood and semen. J Clin Pharmacol 1984;24(2-3):120-126. View abstract.

DiBaise, J. K. A randomized, double-blind comparison of two different coffee-roasting processes on development of heartburn and dyspepsia in coffee-sensitive individuals. Dig.Dis.Sci 2003;48(4):652-656. View abstract.

Hasani-Ranjbar, S., Nayebi, N., Larijani, B., and Abdollahi, M. A systematic review of the efficacy and safety of herbal medicines used in the treatment of obesity. World J Gastroenterol. 7-7-2009;15(25):3073-3085. View abstract.

Quinlan, P., Lane, J., and Aspinall, L. Effects of hot tea, coffee and water ingestion on physiological responses and mood: the role of caffeine, water and beverage type. Psychopharmacology (Berl) 1997;134(2):164-173. View abstract.

Svikis, D. S., Berger, N., Haug, N. A., and Griffiths, R. R. Caffeine dependence in combination with a family history of alcoholism as a predictor of continued use of caffeine during pregnancy. Am J Psychiatry 2005;162(12):2344-2351. View abstract.

Yong-Kee, C. J., Salomonczyk, D., and Nash, J. E. Development and Validation of a Screening Assay for the Evaluation of Putative Neuroprotective Agents in the Treatment of Parkinson's Disease. Neurotox.Res 4-2-2010; View abstract.

Institute of Medicine. Caffeine for the Sustainment of Mental Task Performance: Formulations for Military Operations. Washington, DC: National Academy Press, 2001. Available at: http://books.nap.edu/books/0309082587/html/index.html.

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